tools/patch-image/src/patch-cmdline.c

/*
 * patch-cmdline.c - patch the kernel command line
 *
 * Copyright (C) 2006 Felix Fietkau <nbd@nbd.name>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <string.h>

#define SEARCH_SPACE	(16 * 1024)
#define CMDLINE_MAX		512

int main(int argc, char **argv)
{
	int fd, found = 0, len, ret = -1;
	char *ptr, *p;
	unsigned int search_space;

	if (argc <= 2 || argc > 4) {
		fprintf(stderr, "Usage: %s <file> <cmdline> [size]\n", argv[0]);
		goto err1;
	} else if (argc == 3) {
		fprintf(stdout, "search space used is default of 16KB\n");
		search_space = SEARCH_SPACE;
	} else {
		search_space = atoi(argv[3]);
	}
	len = strlen(argv[2]);
	if (len + 9 > CMDLINE_MAX) {
		fprintf(stderr, "Command line string too long\n");
		goto err1;
	}
	
	if (((fd = open(argv[1], O_RDWR)) < 0) ||
		(ptr = (char *) mmap(0, search_space + CMDLINE_MAX, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) == (void *) (-1)) {
		fprintf(stderr, "Could not open kernel image");
		goto err2;
	}
	
	for (p = ptr; p < (ptr + search_space); p += 4) {
		if (memcmp(p, "CMDLINE:", 8) == 0) {
			found = 1;
			p += 8;
			break;
		}
	}
	if (!found) {
		fprintf(stderr, "Command line marker not found!\n");
		goto err3;
	}

	memset(p, 0, CMDLINE_MAX - 8);
	strcpy(p, argv[2]);
	msync(p, CMDLINE_MAX, MS_SYNC|MS_INVALIDATE);
	ret = 0;

err3:
	munmap((void *) ptr, len);
err2:
	if (fd > 0)
		close(fd);
err1:
	return ret;
}